/* -*- c-basic-offset: 8 -*-
   rdesktop: A Remote Desktop Protocol client.
   Protocol services - Virtual channels
   Copyright 2003 Erik Forsberg <forsberg@cendio.se> for Cendio AB
   Copyright (C) Matthew Chapman <matthewc.unsw.edu.au> 2003-2008
   Copyright 2016 Alexander Zakharov <uglym8@gmail.com>

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "rdesktop.h"
#include <string.h>

#define MAX_CHANNELS            6
#define CHANNEL_CHUNK_LENGTH    1600
#define CHANNEL_FLAG_FIRST      0x01
#define CHANNEL_FLAG_LAST       0x02
#define CHANNEL_FLAG_SHOW_PROTOCOL 0x10

#define MIN(a, b) ((a) < (b) ? (a) : (b))

extern RDP_VERSION g_rdp_version;
extern RD_BOOL g_encryption;

uint32_t vc_chunk_size = CHANNEL_CHUNK_LENGTH;

VCHANNEL g_channels[MAX_CHANNELS];
unsigned int g_num_channels;

VCHANNEL *channel_register(const char *name, uint32_t flags, void (*callback) (STREAM)) {
    if (g_rdp_version < RDP_V5) {
        return NULL;
    }

    if (g_num_channels >= MAX_CHANNELS) {
        logger(Core, Error, "channel_register(), channel table full, increase MAX_CHANNELS");
        return NULL;
    }

    VCHANNEL *channel = &g_channels[g_num_channels];
    channel->mcs_id = MCS_GLOBAL_CHANNEL + 1 + g_num_channels;
    strncpy(channel->name, name, sizeof(channel->name) - 1);
    channel->name[sizeof(channel->name) - 1] = '\0';  // Ensure null-termination
    channel->flags = flags;
    channel->process = callback;
    g_num_channels++;
    return channel;
}

STREAM channel_init(VCHANNEL *channel, uint32_t length) {
    UNUSED(channel);
    STREAM s = sec_init(g_encryption ? SEC_ENCRYPT : 0, length + 8);
    s_push_layer(s, channel_hdr, 8);
    return s;
}

static void channel_send_chunk(STREAM s, VCHANNEL *channel, uint32_t length) {
    uint32_t flags;
    uint32_t thislength;
    RD_BOOL inplace;
    STREAM chunk;

    thislength = MIN(s_remaining(s), vc_chunk_size);

    flags = 0;
    if (length == s_remaining(s)) {
        flags |= CHANNEL_FLAG_FIRST;
    }
    if (s_remaining(s) == thislength) {
        flags |= CHANNEL_FLAG_LAST;
    }
    if (channel->flags & CHANNEL_OPTION_SHOW_PROTOCOL) {
        flags |= CHANNEL_FLAG_SHOW_PROTOCOL;
    }

    logger(Protocol, Debug, "channel_send_chunk(), sending %d bytes with flags 0x%x",
           thislength, flags);

    inplace = (flags & (CHANNEL_FLAG_FIRST | CHANNEL_FLAG_LAST)) == (CHANNEL_FLAG_FIRST | CHANNEL_FLAG_LAST);

    if (inplace) {
        s_pop_layer(s, channel_hdr);
        chunk = s;
    } else {
        chunk = sec_init(g_encryption ? SEC_ENCRYPT : 0, thislength + 8);
    }

    out_uint32_le(chunk, length);
    out_uint32_le(chunk, flags);
    if (!inplace) {
        out_uint8stream(chunk, s, thislength);
        s_mark_end(chunk);
    }
    sec_send_to_channel(chunk, g_encryption ? SEC_ENCRYPT : 0, channel->mcs_id);

    if (inplace) {
        in_uint8s(s, s_remaining(s));
    } else {
        s_free(chunk);
    }
}

void channel_send(STREAM s, VCHANNEL *channel) {
    uint32_t length;

#ifdef WITH_SCARD
    scard_lock(SCARD_LOCK_CHANNEL);
#endif

    s_pop_layer(s, channel_hdr);
    in_uint8s(s, 8);
    length = s_remaining(s);

    logger(Protocol, Debug, "channel_send(), channel = %d, length = %d", channel->mcs_id, length);

    while (!s_check_end(s)) {
        channel_send_chunk(s, channel, length);
    }

#ifdef WITH_SCARD
    scard_unlock(SCARD_LOCK_CHANNEL);
#endif
}

void channel_process(STREAM s, uint16_t mcs_channel) {
    uint32_t length, flags;
    uint32_t thislength;
    VCHANNEL *channel = NULL;
    unsigned int i;
    STREAM in;

    for (i = 0; i < g_num_channels; i++) {
        channel = &g_channels[i];
        if (channel->mcs_id == mcs_channel) {
            break;
        }
    }

    if (i >= g_num_channels) {
        return;
    }

    in_uint32_le(s, length);
    in_uint32_le(s, flags);
    if ((flags & CHANNEL_FLAG_FIRST) && (flags & CHANNEL_FLAG_LAST)) {
        channel->process(s);
    } else {
        in = &channel->in;
        if (flags & CHANNEL_FLAG_FIRST) {
            s_realloc(in, length);
            s_reset(in);
        }

        thislength = s_remaining(s);
        out_uint8stream(in, s, thislength);

        if (flags & CHANNEL_FLAG_LAST) {
            s_mark_end(in);
            s_seek(in, 0);
            channel->process(in);
        }
    }
}